Related Experiment Videos
Studies of the ocular pulse in primates
T W Mittag1, J Serle, R Schumer
1Department of Ophthalmology, Mount Sinai School of Medicine, New York, New York.
Survey of Ophthalmology
|May 1, 1994
Summary
Ocular pulse amplitude (OPA) may be autoregulated in normal and ocular hypertension individuals. However, elevated intraocular pressure (IOP) in glaucoma models disrupts this regulation, suggesting potential vascular abnormalities in low-tension glaucoma.
Area of Science:
- Ophthalmology
- Physiology
- Vascular Biology
Background:
- Intraocular pressure (IOP) and ocular pulse amplitude (OPA) are critical indicators in glaucoma and ocular hypertension (OHT).
- Understanding the relationship between IOP, OPA, and ocular perfusion is vital for diagnosing and managing glaucomatous conditions.
- Previous research suggests potential links between ocular vascular factors and glaucoma, particularly in low-tension glaucoma (LTG).
Purpose of the Study:
- To investigate the relationship between ocular pulse amplitude (OPA) and intraocular pressure (IOP) in various ocular conditions and after interventions.
- To determine if OPA is autoregulated in human subjects with different IOP levels and in animal models of glaucoma.
- To explore potential ocular vascular abnormalities in low-tension glaucoma (LTG).
Main Methods:
- Measurements of OPA and IOP in human subjects with primary open-angle glaucoma (POAG), OHT, LTG, retinal degenerations (RD), and normal controls.
- Pharmacological interventions in OHT volunteers using epinephrine, pilocarpine, timolol, and p-amino-clonidine.
- Assessment of IOP, OPA, and calculated ocular perfusion pressure in normal subjects before and after exercise.
- Evaluation of peak pulse volume (PPV) in laser-induced glaucomatous monkey eyes with elevated IOP, before and after drug treatment.
Main Results:
- OHT subjects exhibited significantly higher IOP and OPA compared to normal controls.
- OPA was significantly lower in LTG and RD subjects compared to normal controls.
- Antiglaucoma drug treatments lowered IOP in OHT subjects without significantly altering OPA.
- Exercise in normal volunteers lowered IOP and increased ocular perfusion pressure but did not change OPA.
- In monkey eyes with elevated IOP, PPV increased when IOP was reduced by 5 mmHg or more with specific drug treatments.
Conclusions:
- OPA may be physiologically autoregulated in human subjects within the normal IOP range (11-21 mmHg).
- LTG might be associated with an ocular vascular abnormality, as indicated by lower OPA.
- Laser-induced glaucoma in monkeys with high IOP (30-35 mmHg) demonstrated a lack of autoregulation, with PPV increasing upon IOP reduction.
- These findings highlight differences in OPA regulation between physiological IOP ranges and experimentally induced high IOP states.